1. Field of the Invention
The present invention relates to a power window apparatus with a pinch detecting function, and more particularly, to an apparatus setting a start cancellation period in which pinch detection is not performed, according to whether a backlash (allowance) exists in a motor that raises and lowers a window and in a window driving mechanism that connects the window to the motor, thereby more reliably detecting a pinch of a foreign object.
2. Description of the Related Art
A power window apparatus with a pinch detecting function has been proposed. When a pinching of a foreign object occurs when a window is raised or lowered by driving force of a motor, the power window apparatus controls the motor to perform a process for avoiding the pinching, which stops or reversely rotates the motor. The power window apparatus includes a pulse encoder that generates pulse signals according to the rotation of the motor, a monitoring unit that monitors the number of revolutions of the motor on the basis of the pulses output from the pulse encoder during the rising of the window, a detecting unit that detects the pinching in a case in which the relative decrement of the number of revolutions of the motor exceeds a predetermined determination reference value during the rising of the window, and a determination reference changing unit that increases a determination reference value during a period from the time when the window starts rising after the lowering of the window to the time when the motor is rotated at a predetermined number of revolutions, as a device having a countermeasure against the backlash (allowance) of a driving device (for example, JP-A-07-113375).
According to the power window apparatus with a pinch detecting function, the determination reference value is increased by the determination reference-changing unit during the period from the time when the window starts rising after the lowering of the window to the time when the motor is rotated at a predetermined number of revolutions. Therefore, the motor rotates at high speed as a state close to unloaded condition in the early period when the window is reversed from the lowering to the rising thereof by the backlash of the driving system from the motor to the window. After that, the number of revolutions of the motor decreases to be stabilized, which is hardly detected as the occurrence of the pinching. Furthermore, since the power window apparatus with a pinch detecting function does not prohibit the determination of the pinching even during the period in which the determination reference value increases, it is possible to use a function as an operation for preventing the pinching.
In addition, in a technology disclosed in Japanese Unexamined Patent Application Publication No. 07-113375, the determination of the pinching is not prohibited in the early period even when the window is reversed from the lowering to the rising thereof, and a function as an operation for preventing the pinching is used. However, another power window apparatus with a pinch detecting function has been proposed. Another power window apparatus sets, as a start cancellation period, a predetermined period from the time when the motor is started to the time when the number of revolutions of the motor reaches a stable point, and does not determine whether a pinching occurs in the window in the period.
Meanwhile, the backlash occurring in the driving system has different sizes according to the vehicles, depending on the accuracy when the motor and the window driving mechanism are manufactured and assembled to a vehicle. Furthermore, the size of the backlash varies with time. In addition, the backlash is large when the window is reversed from the lowering to the rising thereof. The backlash is small when the window rises again after the rising thereof.
On the other hand, in the technology disclosed in Japanese Unexamined Patent Application Publication No. 07-113375, the determination reference value is increased for a predetermined time after the motor is started. However, the ‘period in which the number of revolutions reaches a predetermined number of revolutions’ is a predetermined period prescribed in each power window apparatus, and the ‘determination reference’ is a fixed value selected from a range of 1.5 to 4 times of a general determination reference. As described above, since a variation exists in the size of the backlash of the driving system shown in each vehicle, the ‘period in which the number of revolutions reaches a predetermined number of revolutions’ and the ‘determination reference’ must correspond to the upper limit of the distribution of the backlash. Consequently, it is regarded that the ‘period when the number of revolutions reaches the predetermined number of revolutions’ cannot but be set as a substantially long period, and the ‘determination reference’ cannot but be set as a substantially large value. As a result, it is possible to determine whether the pinching occurs or not soon after the reverse of a door glass, which causes problems in that the reliability thereof is lowered and the period is lengthened. Furthermore, the conventional technology has a countermeasure without exception only when the window is reversed from the lowering to the rising thereof. However, there are times when the backlash is small even when the window is reversed from the lowering to the rising thereof, and when the backlash is large even when the window rises again after the rising thereof.
In addition, the power window apparatus with a pinch detecting function, which sets the predetermined period from when the motor is started to when the number of revolutions of the motor reaches a stable point as a start cancellation period and does not perform the determination of the pinching in the period, has also a problem in that the start cancellation period is lengthened.